@TakingBackGunch: I was only telling our expceriences on our server. And we had some people with the problem. Then hit the command and it wont work. But then we changed our graphic settings and it worked (command + client side graphic change: field of view and view distance seams to be the important changes). Did you hit the command while the player tried to connect or was online ? Use /tpo only when the player is offline.
We had the problem too, that our admins cant login, our solution we gave admin rights to another player to use the command for our admins.